diff --git a/src/SharpMetal/Metal/MTLDevice.cs b/src/SharpMetal/Metal/MTLDevice.cs
index e9e3237..5813e99 100644
--- a/src/SharpMetal/Metal/MTLDevice.cs
+++ b/src/SharpMetal/Metal/MTLDevice.cs
@@ -254,6 +254,7 @@ public partial struct MTLDevice: IDisposable
     {
         [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
         private delegate void NewLibraryCompletionHandler(IntPtr block, IntPtr library, IntPtr error);
+        private NewLibraryCompletionHandler _handler;
 
         public IntPtr NativePtr;
         public static implicit operator IntPtr(MTLDevice obj) => obj.NativePtr;
@@ -468,8 +469,8 @@ public MTLLibrary NewLibrary(NSString source, MTLCompileOptions options, ref NSE
 
         public void NewLibrary(NSString source, MTLCompileOptions options, Action<MTLLibrary, NSError> callback)
         {
-            NewLibraryCompletionHandler handler = (_, library, error) => callback(new MTLLibrary(library), new NSError(error));
-            var block = Block.GetBlockForDelegate(handler);
+            _handler = (_, library, error) => callback(new MTLLibrary(library), new NSError(error));
+            var block = Block.GetBlockForDelegate(_handler);
 
             ObjectiveCRuntime.objc_msgSend(NativePtr, sel_newLibraryWithSourceoptionscompletionHandler, source, options, block);
         }
diff --git a/src/SharpMetal/SharpMetal.csproj b/src/SharpMetal/SharpMetal.csproj
index 79f51cd..1a17d20 100644
--- a/src/SharpMetal/SharpMetal.csproj
+++ b/src/SharpMetal/SharpMetal.csproj
@@ -7,7 +7,7 @@
         <AssemblyName>SharpMetal</AssemblyName>
         <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
         <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
-        <Version>1.0.0-preview16</Version>
+        <Version>1.0.0-preview17</Version>
         <Description>Handcrafted Metal bindings for C#</Description>
         <RepositoryUrl>https://github.com/IsaacMarovitz/SharpMetal</RepositoryUrl>
         <RepositoryType>git</RepositoryType>